System and method for wireless power networking

ABSTRACT

A system for wireless power networking, preferably including one or more nodes, such as transmit nodes, receive nodes, relay nodes, and/or hybrid nodes. The system may function to form a power network (e.g., mesh network) configured to transfer power wirelessly between nodes of the system. A method for wireless power networking, preferably including transmitting power, controlling relay nodes, and/or receiving power, and optionally including optimizing power network operation. The method is preferably performed at (e.g., by one or more nodes of) the system, but can additionally or alternatively be performed by any other suitable system(s).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 17/720,084, filed on 13 Apr. 2022, which claims the benefit of U.S. Provisional Application Ser. No. 63/174,992, filed on 14 Apr. 2021, and of U.S. Provisional Application Ser. No. 63/319,226, filed on 11 Mar. 2022, each of which is incorporated in its entirety by this reference.

STATEMENT OF GOVERNMENT SUPPORT

This invention was made with government support under Contract No. FA8650-21-C-C314 awarded by the Air Force Research Laboratory. The government has certain rights in the invention.

TECHNICAL FIELD

This invention relates generally to the wireless power field, and more specifically to a new and useful system and method for wireless power networking.

BACKGROUND

Typical point-to-point wireless power links are limited in the range over which power can be efficiently transmitted, and may require and/or benefit from unobstructed (e.g., line-of-sight) transmission paths. Thus, there is a need in the wireless power field to create a new and useful system and method for wireless power networking.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A-1H are schematic representations of a various examples of an embodiment of a system for wireless power networking.

FIG. 2A is a schematic representation of an embodiment of a method for wireless power networking.

FIG. 2B is a schematic representation of an example of the method.

FIG. 3A is an isometric view of an embodiment of a metasurface of the system.

FIG. 3B is a detail isometric view of a portion of an example of the metasurface.

FIG. 4A is an isometric view of an embodiment of an impedance sheet of the metasurface.

FIG. 4B is a plan view of a specific example of the impedance sheet.

FIG. 4C is a detail plan view of a reactive cell of the impedance sheet depicted in FIG. 4B.

FIG. 4D is a schematic representation of an equivalent network corresponding to the reactive cell depicted in FIG. 4C.

FIGS. 5A-5C are schematic representations of a first, second, and third specific example, respectively, of a reactive cell.

FIG. 5D is a schematic representation of a specific example of reactive cells of three impedance sheets.

FIGS. 6A-6B are a front view and a side view, respectively, of an example of a relay node of the system.

FIG. 6C is a side view of a variation of the example of the relay node.

FIGS. 7A-7B are schematic representations of examples of portions of the method.

FIG. 7C is a schematic representation of an example of the method.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiments of the invention is not intended to limit the invention to these preferred embodiments, but rather to enable any person skilled in the art to make and use this invention.

1. Overview.

A system 10 for wireless power networking preferably includes one or more nodes 11 (e.g., as shown in FIGS. 1A-1E). The system preferably functions to form a power network (e.g., mesh network) configured to transfer power wirelessly between nodes of the system, preferably via transmission (e.g., at one or more transmit nodes) and reception (e.g., at one or more receive nodes) of propagating electromagnetic radiation (e.g., propagating radio frequency (RF) modes).

A method 20 for wireless power networking preferably includes transmitting power S210, controlling relay nodes S220, and/or receiving power S230, and optionally includes optimizing power network operation S240 (e.g., as shown in FIGS. 2A-2B and/or 7C). The method 20 is preferably performed at (e.g., by one or more nodes of) the system 10, but can additionally or alternatively be performed by any other suitable system(s).

In some examples, the system 10 and/or method 20 can include one or more elements such as described in U.S. patent application Ser. No. 17/028,408, filed 23 Sep. 2020 and titled “METHOD AND SYSTEM FOR WIRELESS POWER DELIVERY”; U.S. patent application Ser. No. 17/015,473, filed 9 Sep. 2020 and titled “SYSTEM AND METHOD FOR WIRELESS POWER RECEPTION”; U.S. patent application Ser. No. 17/006,242, filed 28 Aug. 2020 and titled “METHOD AND SYSTEM FOR WIRELESS POWER DELIVERY”; U.S. patent application Ser. No. 16/706,131, filed 6 Dec. 2019 and titled “METHOD AND SYSTEM FOR WIRELESS POWER DELIVERY”; U.S. patent application Ser. No. 16/539,288, filed 13 Aug. 2019 and titled “METHOD AND SYSTEM FOR WIRELESS POWER DELIVERY”; and/or U.S. patent application Ser. No. 16/899,473, filed 11 Jun. 2020 and titled “METHODS AND SYSTEMS FOR MULTI-OBJECTIVE OPTIMIZATION AND/OR WIRELESS POWER DELIVERY”, each of which is herein incorporated in its entirety by this reference. For example, the system 10 can include one or more ‘transmitters’ and/or ‘receivers’ such as described in U.S. patent application Ser. No. 17/028,408 (e.g., wherein each ‘transmitter’ or ‘receiver’ as described in U.S. patent application Ser. No. 17/028,408 is, or is included in, a different node 11 of the system 10), and/or the method 20 can include transmitting power such as described in U.S. patent application Ser. No. 17/028,408 regarding the ‘method for wireless power delivery’ and/or one or more elements thereof (e.g., transmitting power S210 can include ‘determining transmitter-receiver proximity S100’, ‘determining transmission parameter values S200’, and/or ‘transmitting power based on the transmission parameter values S300’ as described in U.S. patent application Ser. No. 17/028,408).

2. System.

As described above, the system preferably includes one or more nodes 11. The nodes can include one or more: transmit nodes 11 a, receive nodes 11 b, and/or relay nodes 11 c (and/or any other suitable nodes). The transmit nodes 11 a preferably function to transfer power via transmission of propagating electromagnetic radiation (e.g., transmit RF power) to other nodes of the system. The receive nodes 11 b preferably function to receive power via reception of propagating electromagnetic radiation (e.g., receive RF power) from other nodes of the system. The relay nodes 11 c preferably function to relay power transmissions between other nodes of the system.

In some examples, some or all nodes 11 of the system can be hybrid nodes configured to perform multiple functions, such as transmitting, receiving, and/or relaying. For example, a relay node can additionally or alternatively be configured to transmit and/or receive, such as concurrent with and/or at different times from performing a relay function. In a first specific example, this can include splitting incident power into a relayed portion (e.g., redirected as described in more detail regarding the relay nodes 11 c) and a received portion (e.g., converted into electrical power at the node, such as described in more detail regarding the receive nodes 11 b), such as shown byway of examples in FIGS. 7B-7C. In a second specific example, this can include relaying incident power while also transmitting additional power (e.g., both redirecting the incident power into and adding more power into a desired output beam, such as shown by way of example in FIG. 7A). In some examples, a node may be configured to either transmit or receive power (e.g., optionally while also relaying power), but not both, whereas in other examples, a node may have bidirectional capabilities (e.g., being configured to either transmit or receive power, optionally while also relaying power).

In some examples, one or more nodes of the system (e.g., transmit nodes and/or relay nodes) are operable to produce beam-like RF modes (e.g., Gaussian beams, Bessel beams, hybrids thereof, and/or approximations thereof, etc.), such as described below in more detail regarding the method 20.

Some or all nodes can optionally include a wireless communication module, but can additionally or alternatively include wired communication modules or any other suitable communication modules, or can omit communication modules. The wireless communication modules preferably support (e.g., enable communication using) one or more wireless communication protocols (e.g., WiFi, Bluetooth, BLE, NFC, RF, IR, Zigbee, Z-wave, etc.).

Each node (or a subset thereof) can include one or more controllers configured to control node operation (e.g., configure node operation mode, such as controlling the node between transmit, receive, relay, and/or hybrid modes of operation; configure node parameters, such as power transmission, modulation, and/or reception parameters; control communication with other nodes and/or other elements of the system; etc.). However, the receive nodes can additionally or alternatively be controlled in any other suitable manner, and/or can be uncontrolled or substantially uncontrolled.

However, the transmitters and receivers can additionally or alternatively include any other suitable elements.

In a first example, the system can include one transmit node 11 a, one receive node 11 b, and one or more relay nodes 11 c arranged between the transmit node and the receive node (e.g., as shown in FIGS. 1F-1H). In a second example, the system can include one transmit node 11 a, a plurality of receive nodes 11 b, and one or more relay nodes 11 c arranged between the transmit node and the receive nodes (e.g., as shown in FIG. 1C). In a third example, the system can include a plurality of transmit nodes 11 a, one or more receive nodes 11 b, and one or more relay nodes 11 c arranged between some or all of the transmit and receive nodes (e.g., as shown in FIG. 1D).

In some examples, the nodes may have an arbitrary and/or dynamic arrangement with respect to each other. In one example, the system includes one or more transmit nodes (e.g., with fixed positions), one or more receive nodes that undergo numerous changes in position and orientation (e.g., with respect to the transmitter, each other, etc.) over time, and one or more relay nodes that may have fixed or varying positions. The system can optionally be arranged in a setting in which other nearby objects (e.g., obstacles to wireless power transmission) can also have an arbitrary and/or dynamic arrangement with respect to the elements of the system. However, the system can define any other suitable arrangements.

However, the system can additionally or alternatively include any other suitable number of nodes of any suitable type, having any suitable arrangement.

2.1 Transmit Node.

As described above, the transmit nodes 11 a preferably function to transmit RF power to one or more other nodes of the system.

In some embodiments, the transmit nodes of the system can include one or more antennas (e.g., configured to transmit electromagnetic radiation, such as RF and/or microwave power), preferably defining a controllable (e.g., adaptive) antenna array (e.g., linear array, planar array, 3-D array, etc.; phased array, electronically controllable array, etc.).

The antenna array preferably includes a plurality of active antennas (e.g., antennas configured to be actively driven by feeds), more preferably independently controllable active antennas (e.g., wherein each active antenna can be individually controlled independent of all other active antennas of the system; wherein groups of active antennas can be controlled together, wherein each group is controllable independently from all other groups; etc.). In a first variation, the amplitude and/or phase at which each active antenna is driven can be independently controlled (e.g., via a separate IQ modulator or phase shifter for each active antenna). In a second variation, the active antennas are separated into one or more antenna groups, wherein the antennas of a group are controlled together (e.g., via a single IQ modulator or phase shifter for each group). For example, the antennas of a group can have a fixed phase offset (e.g., zero offset, such as wherein all antenna of the group have the same phase as each other; non-zero offset; etc.) with respect to each other (e.g., wherein the fixed phase offset is defined by differences in trace lengths between the IQ modulator or phase shifter and each antenna). However, the active antennas can additionally or alternatively be configured in any other suitable manner.

The antenna array can additionally or alternatively include one or more passive antennas (e.g., configured to electrically and/or resonantly couple to one or more of the active antennas, thereby altering antenna array transmission characteristics). In one example, the system is configured to control (e.g., via switches, such as software-controlled switches; via elements with variable electrical properties, such as variable capacitors; etc.) electrical coupling (e.g., connection, resonant coupling, etc.) and/or decoupling of one or more of the passive antennas to one or more electrical components (e.g., passive components, such as resistors, capacitors, and/or inductors; antennas, such as one or more of the active antennas and/or other passive antennas; etc.). In a first example, a plurality of passive antennas can be electrically connected to and/or disconnected from each other (e.g., via switches operable to electrically connect two or more such antennas). In a second example, variable capacitors (e.g., varactors) and/or other variable (e.g., continuously-variable) elements are electrically coupled (e.g., electrically connected) to one or more passive antennas, enabling control of the loading of the passive antennas and/or their coupling to other antennas (e.g., other passive antennas, active antennas, etc.) in the array and/or their feeds (e.g., wherein varying the properties of one or more of the variable elements coupled to the antennas can function to control the net pattern of the array). In a specific example of this second example, an adaptive antenna array includes a single active antenna and a plurality of passive antennas, wherein one or more of the passive antennas are electrically coupled to one or more variable components.

Each transmit node is preferably electrically connected (e.g., via wired connections, inductive coupling, etc.) to one or more electrical power sources (e.g., power storage elements such as batteries and/or supercapacitors, generators such as internal combustion engine-based generators and/or steam turbines, utility-scale power grids, etc.), and is preferably operable to draw power from the one or more electrical power sources in order to power the transmit node. However, the transmit nodes can additionally or alternatively have any other suitable power connections.

Each transmit node preferably includes one or more controllers configured to control transmit node operation (e.g., control transmission, such as controlling the phased array to transmit propagating radiation of one or more desired modes, control communication with other nodes and/or other elements of the system, etc.). However, the transmit nodes can additionally or alternatively be controlled in any other suitable manner.

In some examples, each transmit node 11 a (or a subset thereof) can include one or more elements such as described in U.S. patent application Ser. No. 17/028,408, filed 23 Sep. 2020 and titled “METHOD AND SYSTEM FOR WIRELESS POWER DELIVERY” which is herein incorporated in its entirety by this reference. For example, a transmit node 11 a can include (or be) a ‘transmitter’ (or one or more elements thereof, such as the one or more antennas) such as described in U.S. patent application Ser. No. 17/028,408.

However, the system can additionally or alternatively include any other suitable transmit nodes having any other suitable elements.

2.2 Receive Node.

As described above, the receive nodes 11 b preferably function to receive RF power from one or more other nodes of the system.

In some embodiments, the receive nodes of the system can include one or more antennas (e.g., configured to receive electromagnetic radiation transmitted by the transmitters). The receivers can optionally include and/or be electrically coupled to (e.g., configured to deliver electrical power to) one or more client devices (e.g., batteries and/or battery-containing devices, such as electrical and/or electronic user devices). Each receive node can optionally include one or more buffer energy stores (e.g., batteries, capacitors such as supercapacitors, etc.), such as a battery electrically coupled between the antenna(s) and the client device (e.g., between the antenna(s) and an electrical output configured to connect to the client device), which can function as a buffer between the antennas (which may provide power at an uneven rate and/or with uneven characteristics) and the client device (which may require and/or benefit from power provision at a substantially constant rate and/or with substantially constant characteristics, which may be temporarily disconnected from the receive node, etc.).

Each receive node can optionally include one or more controllers configured to control receive node operation (e.g., control power reception and/or handling, such as controlling antenna tuning, impedance matching, rectification, and the like; control communication with other nodes and/or other elements of the system; etc.). However, the receive nodes can additionally or alternatively be controlled in any other suitable manner, and/or can be uncontrolled or substantially uncontrolled.

In some examples, each receive node 11 b (or a subset thereof) can include one or more elements such as described in U.S. patent application Ser. No. 17/028,408, filed 23 Sep. 2020 and titled “METHOD AND SYSTEM FOR WIRELESS POWER DELIVERY”, and/or in U.S. patent application Ser. No. 17/015,473, filed 9 Sep. 2020 and titled “SYSTEM AND METHOD FOR WIRELESS POWER RECEPTION”, each of which is herein incorporated in its entirety by this reference. For example, a receive node 11 b can include (or be) a ‘receiver’ (or one or more elements thereof, such as the one or more antennas and/or client devices) as described in U.S. patent application Ser. No. 17/028,408, and/or can include (or be) the ‘system 100 for wireless power reception’ (or one or more elements thereof, such as the ‘antennas 110’, ‘dynamic impedance matches 120’, ‘RF-DC converters 130’, ‘DC impedance converters 140’, and/or ‘DC power outputs 150’) as described in U.S. patent application Ser. No. 17/015,473.

However, the system can additionally or alternatively include any other suitable receive nodes having any other suitable elements.

2.3 Relay Node.

As described above, the relay nodes 11 c preferably function to relay power transmissions between other nodes of the system. For example, an RF power transmission from a transmit node (or from an upstream relay node) can be relayed by the relay node toward a receive node (or a downstream relay node).

In a first embodiment, the relay nodes can function to receive (e.g., absorb) and re-transmit RF power. In this embodiment, each relay node can include one or more phased arrays (e.g., wherein the relay node absorbs the received power and uses it to drive the phased array to re-transmit the power).

In a second embodiment, the relay nodes can function to modulate (e.g., redirect, refocus, etc.) RF power transmissions incident upon them (e.g., without absorbing the RF power, aside from parasitic absorption). In this embodiment, the relay node can include one or more phase-shifting surfaces, such as transmit arrays, reflect arrays, and/or hybrids thereof. In some examples, the phase-shifting surfaces can include one or more metasurfaces 100 (and/or any other suitable metamaterial elements), such as described below in more detail.

Each relay node preferably includes one or configurable elements (e.g., wherein the configurable elements can be actively controlled to change the properties of the outgoing RF power). However, the relay node can alternatively include only fixed and/or passive elements, such as wherein the properties of the outgoing RF power are substantially unchanged during use of the relay node (or are substantially changed only by the characteristics of the incoming RF power incident on the relay node). However, the relay nodes can additionally or alternatively include any other suitable elements with any other suitable functionalities.

As described above, relay nodes operable to modulate RF power transmissions can include one or more metasurfaces 100 (e.g., as shown in FIG. 3A). The metasurface (e.g., metamaterial slab, preferably of subwavelength thickness, including a plurality of polarizable meta-atoms of subwavelength size) can function to modulate RF power transmissions (e.g., of a particular wavelength or wavelength range) that are incident on the metasurface, such as to redirect and/or refocus the incident RF power (e.g., into one or more beam-like modes), preferably directing this power toward another mesh node (or multiple other mesh nodes) of the system. The metasurface can be a Huygens metasurface (e.g., bianisotropic Huygens metasurface), but can additionally or alternatively be any other suitable metasurface. In one example, in which a beam-like mode (e.g., Gaussian beam) is directed toward a relay node by an upstream node, the metasurface can function to redirect and refocus the beam-like mode toward a downstream node (e.g., into a Gaussian beam having different characteristics from the Gaussian beam incident on the relay node).

The metasurface 100 preferably includes a plurality of impedance sheets 101. In some embodiments, the metasurface includes three or more impedance sheets 101, such as three or more substantially parallel impedance sheets. The impedance sheets are preferably separated from each other in space (e.g., by air, dielectric, insulator, etc.), such as shown by way of example in FIG. 3B. The separation between impedance sheets can be uniform or non-uniform, or the impedance sheets can be arranged in any other suitable manner.

The impedance sheets can function to enable modulation of the incident RF power. In some examples, a metasurface having three or more impedance sheets can enable substantially arbitrary modulation (or an approximation thereof, such as an approximation limited by in-plane spatial discretization of the impedance sheets). For example, controlling the impedance of the three impedance sheets can correspond analogously to controlling three material properties of the metasurface, such as the magnetic surface admittance, electric surface impedance, and magnetoelectric coupling coefficient. In examples in which the metasurface includes more than three impedance sheets, these additional impedance sheets can provide additional degrees of freedom, which may enable a range of “degenerate” tuning configurations for any given desired modulation properties (e.g., desired phase shift imposed on incident RF power), as opposed to situations in which exactly three impedance sheets may lead to exactly one tuning configuration that corresponds to the desired properties (e.g., phase shift imposed). In contrast, metasurfaces including fewer than three impedance sheets (e.g., one impedance sheet or two impedance sheets) may not be able to achieve arbitrary modulation, but may still be able to achieve some degree of control over the modulation of incident RF power.

Each sheet preferably includes a plurality of reactive cells 110 (e.g., as shown in FIGS. 4A-4B). The reactive cells preferably function to present a particular (e.g., arbitrary and/or tunable) electromagnetic reactance to incident RF power (e.g., of a particular frequency). Each reactive cell preferably includes one or more electromagnetic resonator networks, such as inductor-capacitor (LC) networks that include at least one inductive element and at least one capacitive element. In one embodiment, each cell includes a parallel LC network, such as shown by way of example in FIGS. 4B-4D, which depicts an example cell structure and a corresponding equivalent network diagram. Parallel LC networks can offer favorable tunability properties, as (in an idealized case) their reactance (as a function of inductance and/or capacitance) includes a pole and two zeros (one approached from the negative side and the other from the positive side), which can enable tunability over a broad range of reactances. In alternate embodiments, one or more cells (e.g., all cells) can include one or more series LC networks and/or series-parallel LC networks. However, the cells can additionally or alternatively include any other suitable resonator networks.

Each resonator network is preferably tunable (e.g., configured to be actively controlled). For example, each resonator network can include one or more variable components (e.g., arranged in the inductive and/or capacitive path of an LC network, such as a parallel LC network), such as biased variable capacitors (e.g., in which the variable capacitor bias is electrically controlled), reactive elements connected to a switch bank, and/or any other suitable tunable lumped elements. The variable components are preferably arranged at locations of high voltage and/or current (e.g., locations at which the voltage and/or current induced by incident RF power is high, such as locations at which it is maximized or within a threshold fraction of maximal), which can function to increase the effect of these components on the resonant properties of the network, but can additionally or alternatively have any other suitable arrangement. In one example, each resonator network is a parallel LC network that includes a variable component (e.g., varicap and/or other component operable to alter its capacitance) connected along its inductive path.

In some embodiments, the variable components can include tunable capacitive elements and/or components operable to tune any other suitable electromagnetic properties, switch between different operation modes, and/or otherwise affect the resonance properties of the resonator network. In examples, these components can include one or more: diode varactors, MEMS varactors, liquid crystal-based components, liquid metal-based components, liquid dielectric-based components, phase transition material-based components, PIN diodes, MEMS switches, dielectric actuator-based components, ferrite-based components, piezoelectric-based components, components based on one or more electrically and/or magnetically polarizable structures, and/or any other suitable component types. For example, the effective dielectric constant of the substrate may be tuned through one or more of: piezoelectric structures, liquid crystals, electrically and/or magnetically polarizable structures, and/or any other suitable structures.

Diode varactors can be controlled by application of a bias voltage, which can function to control the varactor capacitance (e.g., wherein continuous control of the applied voltage leads to continuous control of the resulting capacitance). In some examples, the intrinsic diode resistance may result in high losses.

MEMS varactors can be controlled by control signals that function to select between discrete capacitance values (e.g., wherein fine-grained control between many such values may be achieved), often with low losses. Some examples of these components may be relatively expensive, and so may be undesirable for use in some cost-sensitive applications.

Liquid crystal-based components can be controlled by application of a (quasi-static) electric field, which alters the liquid crystal's dielectric constant (e.g., and thus, the capacitance of the component). These components typically enable very low losses (e.g., even at high frequencies, such as RF) and continuous tunability (e.g., wherein continuous control of the applied electric field strength leads to continuous control of the dielectric constant, and thus of the capacitance). In some examples, these components can be expensive and/or complicated to incorporate into standard PCB assemblies.

Liquid metal-based components and liquid dielectric-based components can be controlled by use of applied electric fields and/or other microfluidic techniques to controllably reconfigure metallic and dielectric structures, respectively, thereby altering one or more of the component's electrical properties (e.g., capacitance). These components can typically enable low losses and continuous tunability. In some examples, these components can be complicated to incorporate into standard PCB assemblies.

Phase transition material-based components can be controlled by applying and/or removing heat to induce phase changes in the material, thereby altering its electromagnetic material properties (e.g., conductivity, dielectric constant, etc.) and thus the electrical properties of the component. These components can typically enable high frequency operation. In some examples, these components may cause high losses (e.g., several dB of loss), can be complicated to incorporate into standard PCB assemblies, and/or can be limited in tunability (e.g., offering only binary on/off control).

Switch components (e.g., PIN diodes, MEMS switches, etc.) can function to alter the network impedance, such as by switching the switch state (e.g., wherein, by switching the switch closed or open, one or more other circuit elements and/or conductive regions are electrically coupled to or decoupled from the network, respectively, via the switch). PIN diodes can be operable as switches, wherein a bias voltage can control the diode to switch between a closed state (e.g., wherein the diode is conductive) and an open state (e.g., wherein the network is substantially open across the diode). In some examples, PIN diodes may cause high losses (e.g., several dB of loss), and/or are typically limited in tunability (e.g., offering only binary on/off control). MEMS switches can be controlled by control signals that function to select between an open state and a closed state. Some examples of MEMS switches may be relatively expensive, and so may be undesirable for use in some cost-sensitive applications; further, they are typically limited in tunability (e.g., offering only binary on/off control).

Dielectric actuator-based components (e.g., including one or more dielectric elastomers) can be controlled by application of a (quasi-static) electric field, which alters the dimensions of the dielectric, thereby altering the capacitance of the component (e.g., by changing the distance between the conductive portions). These components can enable low losses and/or continuous tunability (e.g., wherein continuous control of the applied electric field strength leads to continuous control of the dielectric dimensions, and thus of the capacitance). In some examples, these components can be complicated to incorporate into standard PCB assemblies.

Ferrite-based components can be controlled by application of a (quasi-static) magnetic field, which controls the ferrite saturation, and thus the ferrite permeability. Accordingly, the application of the magnetic field can enable control over properties of the component, such as control over its inductance. Although continuous control of the applied magnetic field strength could lead to continuous control of the ferrite permeability, and thus of the component inductance, many ferrite-based components will offer only limited tunability (e.g., offering only binary on/off control). In some examples, these components may cause high losses (e.g., several dB of loss), and/or may require non-negligible amounts of power to control (e.g., due to power requirements associated with generation of the magnetic fields to apply).

However, the resonator networks can additionally or alternatively include any other suitable variable components, and/or some or all of the resonator networks can alternatively include only fixed components.

In some embodiments, the resonator networks can be configured to meet one or more tunability objectives. First, in some examples, the resonator networks can be configured to maximize (and/or exceed a threshold value of) an achievable range of reactances (the imaginary component of the impedance) that can be reached via resonator network tuning (e.g., over the range of tunability afforded by the one or more variable components of the resonator network). For example, the reactance as a function of a variable component parameter (e.g., capacitance) can include and/or approach one or more poles and zeros, thereby sweeping from (or near) zero to (or toward) both positive and negative infinity. Over this range of achievable reactance values (or over a subset thereof, such as a subset corresponding to likely operational ranges), the resonator networks can be configured to enable minimization (and/or reduction to below a threshold value) of resistance (the real component of the impedance). For example, the resonator network parameters can be selected to minimize (or reduce) an integral over the achievable or desired range of reactances (or a weighted integral, weighted based on likely or anticipated frequent operation ranges). In some examples, in which the resonator network includes multiple tunable components, the increased number of degrees of freedom afforded by these multiple components can result in “degenerate” reactances (e.g., wherein a particular reactance value can be achieved by more than one tuning configurations, wherein the different “degenerate” tuning configurations may correspond to different resistance values). In such examples, the system can be configured to operate using the tuning parameters that result in the lowest resistance of all the configurations corresponding to the desired reactance (or to a reactance value sufficiently close to the desired value, such as within a threshold tolerance from the desired value). However, the reactive cells can additionally or alternatively be configured in any other suitable manner.

In a first embodiment of a reactive cell including a parallel LC network, the reactive cell has a metallic structure, such as shown by way of example in FIGS. 4B-4C. In this embodiment, the structure preferably includes two metallic regions with a thin non-conductive strip separating them, thereby defining the capacitive path of the parallel LC network. Additionally, the structure preferably includes a metallic strip (e.g., thin metallic strip) arranged orthogonal (or substantially orthogonal) to the non-conductive strip of the capacitive path, wherein this metallic strip defines an inductive path in parallel with the capacitive path. In some examples, the structure can include a tunable capacitive element (e.g., varicap, such as a surface-mount technology varicap) arranged along the metallic strip (e.g., in series with the metallic strip) of the inductive path. The tunable element is preferably voltage-controlled (but can additionally or alternatively be controlled in any other suitable manner). For example, the structure can include a thin bias conductor running substantially orthogonal to the inductive path, thereby enabling control of the tunable element while reducing interaction of the bias conductor with the RF power present at the node.

In a second embodiment, the reactive cell can be the Babinet equivalent of the structure described above regarding the first embodiment (e.g., as shown in FIGS. 5A-5C). In this embodiment, the structure is the complement of the structure of the first embodiment, wherein metallic regions of the first embodiment are replaced by non-conductive regions, and non-conductive regions of the first embodiment are replaced by metallic regions. In this embodiment, the tunable capacitive element is preferably rotated 90° (relative to its orientation in the first embodiment), thereby capacitively connecting the two parallel metallic strips that bound the non-conductive strip at which the tunable element is located. In a variation of this embodiment (e.g., as shown in FIGS. 5A and/or 5C), the tunable capacitive element is located along the single metallic strip that runs between the parallel metal strips, rather than bridging the non-conductive strip between those two parallel metallic strips.

In a third embodiment, the reactive cell has a dielectric structure. For example, the cell can include one or more dielectric resonators (e.g., dielectric disks) coupled to a transmission line that includes a tunable capacitive element.

However, the impedance sheet can additionally or alternatively include any other suitable reactive cells having any suitable structures and/or arrangements.

Each impedance sheet can include a regular array (e.g., rectangular array) of substantially identical reactive cells 110 (e.g., as shown in FIG. 4B). Alternatively, reactive cells of a sheet can differ from each other and/or have any other suitable arrangement with respect to each other. Further, the sheets can have the same cells and/or arrangement of cells as one another, or each sheet (or a subset thereof) can have different cells and/or cell arrangements from the other sheets.

In a first example, each sheet includes a rectangular array of reactive cells, in which the unit cell dimensions of the array of each sheet are identical (or substantially identical). The reactive cells of the three sheets (or a subset thereof) may be substantially aligned with one another along a reference axis normal to the three sheets (‘normal axis’), wherein features of each cell (e.g., capacitive elements such as separations between conductive pads, inductive elements such as conductive strips, etc.) are aligned along the reference axis with corresponding features of cells of the other sheets (e.g., capacitive elements of the first sheet aligned with corresponding capacitive elements of the other sheets, inductive elements of the first sheet aligned with corresponding inductive elements of the other sheets, etc.). Additionally or alternatively, the cells of one or more sheets may be displaced laterally (e.g., within the plane of the sheet, orthogonal to the reference axis) from those of one or more other sheets, such as displaced (along one or more lateral axes, such as axes defined by the rectangular array and/or axes substantially parallel and/or orthogonal to reactive cell features, such as boundaries between conductive and non-conductive regions), such as displaced by a fractional amount (e.g., ½, ¼, ⅛, ⅓, ⅙, etc.) of a unit cell dimension (e.g., the unit cell dimension corresponding to the lateral axis along which the displacement is defined). In a specific example (e.g., as shown in FIG. 5D), the reactive cells of the first and third sheets are substantially aligned with each other, whereas the reactive cells of the second sheet (arranged between the first and third sheets) is displaced by half the unit cell dimension along one of the lateral axes of the array (e.g., an axis orthogonal to a long axis defined by an inductive element of the reactive cell).

In embodiments in which the metasurface (e.g., or one or more impedance sheets thereof) is not actively tunable (e.g., does not include any tunable elements), the reactive cells of the metasurface can differ from each other in order to achieve the desired (fixed) modulation properties (e.g., fixed lensing behavior), such as refocusing an incident Gaussian beam received from a first node (e.g., transmit node or upstream relay node) into a different Gaussian beam directed toward a third node (e.g., receive node or downstream relay node). For example, the aspect ratios and/or dimensions of the reactive cells and/or the elements thereof can differ between the different reactive cells of the impedance sheet and/or the metasurface; additionally or alternatively, the structure and/or equivalent circuits of some reactive cells may differ from others.

In a variation of these embodiments, in which the metasurface (or one or more elements thereof) is actively tunable, the reactive cells of the metasurface can differ from each other in order to achieve the desired baseline modulation properties (e.g., lensing behavior, such as described above), wherein the tunable elements can be used to control the modulation properties (e.g., control in a property space around the baseline, such as altering one or more characteristics of the lensing behavior). In examples, such control can be used to adapt to (e.g., optimize based on) changing circumstances, such as changes in position and/or modulation properties of one or more upstream and/or downstream nodes, changes in the environment (e.g., introduction, change in position, and/or removal of one or more obstacles, changes in environmental conditions such as temperature and/or humidity, etc.), changes in desired behavior (e.g., reversal of beam transmission direction, change of upstream and/or downstream target, etc.), and/or any other suitable changes. In a specific example, in which the baseline properties are configured to refocus an incident Gaussian beam received from a first node into a different Gaussian beam directed toward a third node, in response to a change in position of the third node, the modulation properties can be controlled to alter the properties of the Gaussian beam so that it is directed toward the new location of the third node; analogously, in response to a change in position of the first node, the modulation properties can be controlled such that the Gaussian beam is still directed toward the third node, despite the change in properties of the incoming Gaussian beam (arising from the change in position of the first node). However, the modulation properties can additionally or alternatively be controlled in any other suitable manner.

However, the metasurface can additionally or alternatively include any other suitable elements in any suitable arrangement.

In some examples (e.g., examples in which the relay node can additionally function as a transmit and/or receive node), the relay node can optionally include one or more feeding structures 1101 (e.g., as shown in FIGS. 6A-6C), such as structures operable to feed power into the metasurface (e.g., to be transmitted, optionally along with redirected power incident on the relay node) and/or receive power from the metasurface (e.g., power incident on the metasurface, which the metasurface redirects toward the feeding structure). The feeding structure(s) can be connected to the metasurface by one or more mechanical supports 1102, and/or by any other suitable elements (but can alternatively not be connected to the metasurface). In such examples, the relay node can optionally include one or more elements such as described above regarding the transmit and/or receive nodes (e.g., to enable and/or facilitate power transmission and/or reception), such as one or more electrical power sources and/or stores.

In some such examples, it may be preferable to include multiple feeding structures in each such relay node, which can increase the efficiency of coupling power into and/or out of the feeding structures (e.g., depending on the properties of the incident power and/or desired properties of the transmitted output power). For example, by including a feeding structure on either side of the metasurface, power incident on the metasurface could be reflected to the feeding structure on the same side of the metasurface, rather than being transmitted through the metasurface, thereby avoiding ohmic losses associated with transmission through the metasurface (and analogously, power to be transmitted in a particular direction can be provided from the feeding structure positioned to enable reflection, rather than transmission). Further, additional feeding structures arranged in different locations could enable further reduction of such losses, in an analogous manner.

Each relay node can optionally include one or more controllers configured to control relay node operation (e.g., control modulation of incident radiation, such as controlling one or more tunable elements of the metasurface(s) to effect desired modulation; control feeding structure operation, such as controlling power input to and/or reception from the metasurface; control communication with other nodes and/or other elements of the system, etc.). However, the relay node can additionally or alternatively be controlled in any other suitable manner, or can be uncontrolled or substantially uncontrolled (e.g., in the case of a non-tunable metasurface).

However, the system can additionally or alternatively include any other suitable elements having any suitable functionality.

3. Method.

As described above, the method 20 for wireless power networking preferably includes transmitting power S210, controlling relay nodes S220, and/or receiving power S230. The method can optionally include optimizing power network operation S240. The method preferably functions to efficiently transmit power wirelessly through a network (e.g., mesh network) of nodes, such as the network defined by the system 10 described above.

3.1 Transmitting Power.

Transmitting power S210 preferably functions to generate one or more RF power transmissions within the network. S210 is preferably performed at one or more transmit nodes. Each transmit node preferably directs a power transmission toward one or more other nodes (e.g., relay nodes, receive nodes, etc.) of the network. The transmit node preferably transmits a beam-like mode (e.g., Gaussian beam, Bessel beam, a hybrid thereof, etc.) directed toward the downstream node. Optionally, the transmit node can generate multiple beam-like modes and/or any other suitable modes (e.g., for transmissions directed toward multiple nodes). However, S210 can additionally or alternatively include transmitting power in any other suitable manner.

3.2 Controlling Relay Nodes.

Controlling relay nodes S220 preferably functions to control one or more relay nodes to relay power transmissions from upstream nodes to downstream nodes. S220 preferably includes controlling each relay node that receives RF power during performance of the method (e.g., power transmitted toward the node in S210, power directed toward the node by one or more other relay nodes in S220, etc.). However, S220 can additionally or alternatively include controlling any other set of one or more relay nodes.

S220 preferably includes controlling a relay node to relay RF power to a downstream node (or nodes) along a desired transmission path (e.g., transmission path from one or more transmit nodes to one or more receive nodes via one or more relay nodes). The relay node is preferably controlled to modulate RF power incident upon it in order to define a beam-like mode directed toward the next node downstream of the relay node being controlled. In examples, the beam-like modes can include Gaussian beams, Bessel beams, hybrids thereof, and/or any other suitable beam-like modes. Optionally, the relay node can be controlled to modulate the incident RF power into multiple beam-like modes and/or any other suitable modes (e.g., in order to relay power simultaneously to multiple downstream nodes).

The relay node is preferably controlled based on: known incident power characteristics (e.g., incoming phase characteristics and/or beam-like mode characteristics); downstream node position (e.g., relative to the relay node being controlled); characteristics of the relay node being controlled and the downstream node, such as characteristics related to the size (e.g., aperture radius, width area, etc.) of the electromagnetic element (e.g., phase-shifting surface, phased array, receiver, etc.) of the nodes and/or any other suitable information.

In some examples, the relay node can be controlled based further on one or more targets for link efficiency between the relay node and the downstream node. For example, for any given desired RF mode, each node of the link can be associated with a respective area coverage fraction (e.g., corresponding to the fraction of power associated with the mode that intersects the aperture of the respective node's electromagnetic element). To meet a particular link efficiency target η, the product of these two area coverage fractions (ϵ_(r), corresponding to the relay node, and ϵ_(d), corresponding to the downstream node) must be greater than the target: ϵ_(r)ϵ_(d)≥η.

In one such example, S220 includes controlling a relay node to direct a Gaussian beam toward the downstream node. In this example (as well as in some other examples), a larger beam waist can be beneficial because a larger beam waist corresponds to a smaller derivative of phase with respect to change in position (e.g., radial position r outward from the beam axis, corresponding to a phase derivative

$\frac{\partial\phi}{\partial r},$

but additionally or alternatively axial position z along the beam axis and/or any other suitable spatial parameter(s)). This smaller phase derivative value can enable a more accurate discretized approximation of the desired mode to be realized at the relay node, wherein a discretization is used to map the desired mode onto the set of discrete reactive cells defining the metasurface. Accordingly, S220 preferably includes controlling the relay node to generate a beam-like mode with a larger beam waist.

In this example, S220 preferably includes determining one or more desired characteristics of the Gaussian beam, such as the focal point location (e.g., distance from the relay node along a line connecting the relay node to the downstream node), the beam waist, the Rayleigh length (or analogously, the confocal parameter/depth of focus), the beam divergence, and/or any other suitable beam characteristics. These characteristics can optionally be determined using a constrained optimization approach. For example, the characteristics can be determined such that the beam waist is maximized, subject to the constraint that the product of the two area coverage fractions is greater than a target link efficiency. In a specific example, in which an aperture i is approximately circular and oriented approximately normal to the beam, the associated area coverage fraction ϵ_(i) can related to the beam radius at the aperture w(z_(i)) based on the approximation

${{w\left( z_{i} \right)} \approx \frac{\sqrt{2}r_{i}}{\sqrt{- {\log\left( {1 - \epsilon_{i}} \right)}}}},$

where r_(i) is the radius of aperture i.

Note that this constraint typically corresponds to a maximum separation between the two nodes, wherein no Gaussian beam approximation can meet or exceed the target link efficiency for nodes separated by a greater distance than this maximum. Accordingly, for a link between nodes separated by more than this maximum, the constraint may need to be relaxed (e.g., by allowing the beam radius at the downstream node to exceed that node's aperture size by a greater amount than typically tolerable) and/or the target link efficiency may need to be revised downward.

A person of skill in the art will recognize that this determination of Gaussian beam characteristics can additionally or alternatively be applied in an analogous manner in performance of S210 (e.g., wherein the transmit node generates the beam-like mode having characteristics determined based on an analogous constrained optimization).

Additionally or alternatively, S220 can include controlling one or more relay nodes to generate one or more other beam-like modes (e.g., Bessel beams, Bessel-Gaussian beams, multi-beam modes, etc.). In examples, characteristics of other beam-like modes can be determined in a manner analogous to the Gaussian beam example described above. Further, S220 can include controlling one or more relay nodes to generate any other suitable RF modes, and/or controlling one or more relay nodes in any other suitable manner.

3.3 Receiving Power.

Receiving power S230 preferably functions to receive the power relayed through the network of nodes. S230 is preferably performed at one or more receive nodes, but can additionally or alternatively be performed at any other suitable elements. In some embodiments, the method can include using the power received in S230 to provide power for one or more electrical devices (e.g., electrical devices electrically coupled to the receive node). For example, the power received can be converted to DC and used to charge an energy store (e.g., battery) connected to the receive node, power a client device connected to the receive node, and/or be used in any other suitable manner. However, S230 can additionally or alternatively include receiving power in any other suitable manner.

3.4 Optimizing Power Network Operation.

Optimizing power network operation S240 can function to improve performance (e.g., efficiency, speed, etc.) of the wireless power network. For example, S240 can include determining and/or modifying operational parameters associated with performance of other elements of the method (e.g., S210, S220, and/or S230).

In some examples, S240 can include optimizing operation of the transmit and/or relay nodes, based on power reception metrics (e.g., sampled by the receive nodes that receive the power). For example, S240 can include performing one or more optimum searches over a parameter space defined by the tunable elements of one or more transmit and/or relay nodes (e.g., phased array elements, tunable metasurface elements, etc.), using one or more objective functions defined based on power received by one or more downstream nodes (e.g., receive nodes). In some examples, the communication modules (e.g., wireless communication modules) of the nodes can be used to communicate power reception metrics, optimum search information, and/or any other suitable information used to perform the optimum search.

For example, S240 can include performing one or more optimum searches (e.g., local searches, global searches such as stochastic global searches, etc.) over one or more parameter spaces (e.g., parameter spaces associated with the transmit node(s), such as associated with phased array parameters, associated with the relay node(s), such as associated with metasurface tuning parameters, etc.), such as by controlling the node(s) based on a parameter value set within the parameter space while transmitting RF power, quantifying the efficiency of RF power transmission to one or more destinations (e.g., receive nodes, relay nodes, etc.), and adjusting the parameter value sets based on these quantifications.

In some such examples, S240 can include optimizing (concurrently, sequentially, and/or with any other suitable relative timing) each node-node link (or a subset thereof) and/or multi-hop segment of the transmission path. In a first such example, S240 can include first optimizing transmit parameters of the transmit node to maximize power incident upon the (first) relay node (e.g., upon the metasurface thereof), then optimizing modulation parameters of that relay node to maximize power incident upon the following node (e.g., downstream relay node, receive node, etc.), and so on. In a variation of this example (e.g., in which the relay node is not operable to quantify and/or communicate power incident upon its metasurface), S240 can include first optimizing transmit parameters of the transmit node to maximize power received at the receive node (e.g., while keeping relay node parameters fixed, while altering relay node parameters only enough to achieve some amount of power transmission to the receive node, etc.), then optimizing modulation parameters of the (first) relay node to maximize power incident upon the receive node, and so on. Additionally or alternatively (e.g., in examples in which the relay node is not operable to quantify and/or communicate power incident upon its metasurface), S240 can include jointly optimizing parameters of multiple nodes (e.g., of the transmit node and the one or more relay nodes defining a transmission path), such as to maximize power received at the receive node(s). However, S240 can additionally or alternatively include performing any other suitable optimizations, based on any suitable information, with any suitable timing.

In some examples, S240 can include determining and/or operating based on one or more charging plans, such as plans that define duty cycles for power delivery to different receive nodes of the system. For example, S240 can include determining charging plan that defines two or more power transmission paths (e.g., a first power transmission path for transmitting power to a first set of receive nodes, a second power transmission path for transmitting power to a second set of receive nodes, etc.) and a duty cycle for each power transmission path (e.g., wherein the method would include transmitting, relaying, and receiving power based on the charging plan, wherein the first power transmission path is utilized for its associated duty cycle, the second power transmission path is utilized for its associated duty cycle, and so on).

In some examples, S240 can include performing one or more elements such as described in U.S. patent application Ser. No. 17/006,242, filed 28 Aug. 2020 and titled “METHOD AND SYSTEM FOR WIRELESS POWER DELIVERY”, which is herein incorporated in its entirety by this reference.

However, S240 can additionally or alternatively include optimizing power network operation in any other suitable manner.

Further, the method 20 can additionally or alternatively include any other suitable elements performed in any suitable manner.

The FIGURES illustrate the architecture, functionality and operation of possible implementations of systems, methods and computer program products according to preferred embodiments, example configurations, and variations thereof. In this regard, each block in the flowchart or block diagrams may represent a module, segment, step, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block can occur out of the order noted in the FIGURES. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

As a person skilled in the art will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the preferred embodiments of the invention without departing from the scope of this invention defined in the following claims. 

We claim:
 1. A system for wireless power networking, the system comprising a relay node, the relay node comprising: a tunable metasurface operable to modulate propagating RF radiation incident upon the tunable metasurface, the tunable metasurface comprising a plurality of impedance sheets, wherein each impedance sheet of the plurality comprises: a plurality of electromagnetic resonator networks; and a plurality of variable electromagnetic components, wherein each variable electromagnetic component of the plurality is electromagnetically coupled to a different electromagnetic resonator network of the plurality and is operable in a plurality of operation modes such that at least one resonance property of the electromagnetic resonator network is altered by transition of the variable electromagnetic component between the operation modes; and a controller is configured to control each variable electromagnetic component of the plurality to transition between the operation modes of the plurality.
 2. The system of claim 1, wherein the relay node further comprises a feeding structure electromagnetically coupled to the tunable metasurface.
 3. The system of claim 2, wherein the relay node is operable to: receive propagating RF radiation at the tunable metasurface; and control the tunable metasurface to modulate the propagating RF radiation such that the relay node: directs a first portion of the propagating RF radiation into the feeding structure, wherein the first portion of the propagating RF radiation is coupled into the feeding structure; and relays a second portion of the propagating RF radiation toward a target location.
 4. The system of claim 3, further comprising a second relay node, the second relay node comprising a second metasurface arranged at the target location.
 5. The system of claim 4, wherein: the second relay node comprises a second feeding structure; the second metasurface comprises a second tunable metasurface configured to modulate the second portion of the propagating RF radiation such that the second relay node: directs a first subportion of the second portion into the second feeding structure, wherein the first subportion is coupled into the second feeding structure; and relays a second subportion of the second portion toward a second target location.
 6. The system of claim 2, wherein the relay node is operable to: receive propagating RF radiation at the tunable metasurface, the propagating RF radiation comprising: a first portion emitted by the feeding structure; and a second portion not emitted by the feeding structure; and control the tunable metasurface to modulate the propagating RF radiation such that the relay node directs a subset of the propagating RF radiation toward a target location.
 7. The system of claim 4, further comprising a second relay node, the second relay node comprising a second metasurface arranged at the target location.
 8. The system of claim 7, wherein: the second relay node comprises a second feeding structure; the second metasurface comprises a second tunable metasurface configured to modulate the subset of the propagating RF radiation such that the second relay node: directs a first subportion of the subset into the second feeding structure, wherein the first subportion is coupled into the second feeding structure; and relays a second subportion of the subset toward a second target location.
 9. The system of claim 1, wherein the metasurface is a bianisotropic Huygens metasurface.
 10. The system of claim 1, wherein the plurality of impedance sheets comprises a first impedance sheet, wherein the plurality of electromagnetic resonator networks of the first impedance sheet defines a substantially regular array on the metasurface.
 11. The system of claim 10, wherein each electromagnetic resonator network of the substantially regular array is substantially identical.
 12. The system of claim 1, wherein the plurality of impedance sheets comprises a first impedance sheet, wherein each electromagnetic resonator network of the first impedance sheet defines a parallel LC network comprising an inductive element and a capacitive element.
 13. The system of claim 12, wherein the plurality of variable electromagnetic components comprises a set of tunable capacitors, wherein each electromagnetic resonator network of the first impedance sheet is electromagnetically coupled to a different tunable capacitor of the set.
 14. The system of claim 13, wherein each electromagnetic resonator network of the first impedance sheet is electromagnetically coupled to the associated tunable capacitor via the inductive element of the electromagnetic resonator network.
 15. The system of claim 14, wherein, for each electromagnetic resonator network of the first impedance sheet, the inductive element comprises a conductive strip electrically connected to the associated tunable capacitor.
 16. The system of claim 1, wherein each variable electromagnetic component of the plurality comprises a tunable capacitor.
 17. The system of claim 16, wherein the controller is configured to independently control the capacitance of each variable electromagnetic component of the plurality.
 18. The system of claim 1, wherein each variable electromagnetic component of the plurality comprises a switch operable to electrically connect a respective reactive element to the electromagnetic resonator network electromagnetically coupled to the variable electromagnetic component.
 19. The system of claim 1, wherein the plurality of impedance sheets comprises three impedance sheets.
 20. The system of claim 1, further comprising a second relay node, the second relay node comprising a second metasurface, wherein: the controller is configured to control the tunable metasurface such that propagating RF radiation incident upon the tunable metasurface is redirected toward the second metasurface; and the second relay node is configured such that propagating RF radiation incident upon the second metasurface is redirected toward the receive node.
 21. The system of claim 20, wherein: the second metasurface comprises a second tunable metasurface, the second tunable metasurface comprising a second plurality of impedance sheets; and the second relay node further comprises a second controller configured to control each impedance sheet of the second plurality.
 22. The system of claim 21, further comprising a network controller configured to communicate control instructions to the controller and to the second controller. 